gethのPub/Subのサンプル

geth_pubsub.go

package main

import (
	"encoding/json"
	"log"
	"net/url"
	"os"
	"os/signal"

	"github.com/gorilla/websocket"
)

// {"id": 1, "method": "eth_subscribe", "params": ["newPendingTransactions"]}
type SubscribeMsg struct {
	Id     int32    `json:"id"`
	Method string   `json:"method"`
	Params []string `json:"params"`
}

// {"jsonrpc":"2.0","id":2,"result":"0x9ce59a13059e417087c02d3236a0b1cc"}
type SubscribeResponseMsg struct {
	JsonRpc string `json:"jsonrpc"`
	Id      int32  `json:"id"`
	Result  string `json:"result"`
}

func main() {
	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt)

	u, err := url.Parse("ws://127.0.0.1:8546")
	if err != nil {
		log.Fatal(err)
	}

	c, _, err := websocket.DefaultDialer.Dial(u.String(), nil)
	if err != nil {
		log.Fatal("dial:", err)
	}
	defer c.Close()

	done := make(chan struct{})

	go func() {
		defer close(done)
		for {
			_, message, err := c.ReadMessage()
			if err != nil {
				log.Println("read:", err)
				return
			}
			log.Printf("recv: %s", message)
		}
	}()

	newPedingTranSubMsg := SubscribeMsg{
		Id:     1,
		Method: "eth_subscribe",
		Params: []string{"newPendingTransactions"},
	}
	sendMsg(c, newPedingTranSubMsg)

	for {
		select {
		case <-done:
			return
		case <-interrupt:
			log.Println("interrupt")
			return
		}
	}
}

func sendMsg(ws *websocket.Conn, msg interface{}) {
	ws.WriteJSON(msg)
	b, _ := json.Marshal(msg)
	log.Printf("Send: %#v\n", string(b))
}